Intake and exhaust valve control strategies to reduce noise/vibration/harshness during engine stop/start events

Abstract

A stop/start system and method for an engine of a vehicle include a valve control system configured for full lift control of respective intake and exhaust valves of a plurality of cylinders of the engine and a controller of the engine configured to perform an engine stop event including initiating a fuel shutoff (FSO) event whereby fueling to the engine is disabled and the engine fully stops after a stop period and, in response to initiating the FSO event, commanding the valve control system to close each intake valve prior to closing its respective exhaust valve to (i) expel any residual gases from the cylinders during respective exhaust strokes prior to closing the respective exhaust valves, and (ii) prevent air-only intake and compression within the cylinders during the stop period to thereby mitigate or eliminate noise/vibration/harshness (NVH) caused by the air-only intake and compression.

1 . A stop/start system for an engine of a vehicle, the stop/start system comprising:
 a valve control system configured for full lift control of respective intake and exhaust valves of a plurality of cylinders of the engine; and   a controller of the engine configured to perform an engine stop event including:
 initiating a fuel shutoff (FSO) event whereby fueling to the engine is disabled and the engine fully stops after a stop period, and 
 in response to initiating the FSO event, commanding the valve control system to close each intake valve prior to closing its respective exhaust valve to:
 (i) expel any residual gases from the cylinders during respective exhaust strokes prior to closing the respective exhaust valves, and 
 (ii) prevent air-only intake and compression within the cylinders during the stop period to thereby mitigate or eliminate noise/vibration/harshness (NVH) caused by the air-only intake and compression. 
 
   
     
     
         2 . The stop/start system of  claim 1 , wherein the commanding of the valve control system comprises closing each exhaust valve after the exhaust stroke of its respective cylinder. 
     
     
         3 . The stop/start system of  claim 1 , wherein the commanding of the valve control system comprises fully closing the intake valves followed by fully closing the respective exhaust valves for the remainder of the stop period until the engine stop event is complete. 
     
     
         4 . The stop/start system of  claim 1 , wherein the NVH is caused by engine jerk corresponding to cylinder pressure increases caused by the air-only intake and compression; and
 wherein the controller is configured to command the valve control system to close every intake valve of the engine prior to closing every respective exhaust valve of the engine to prevent both (i) residual in-cylinder gases and (ii) air-only in-cylinder compression during subsequent exhaust strokes to thereby mitigate or eliminate NVH.   
     
     
         5 . The stop/start system of  claim 1 , wherein the controller is further configured to perform an engine start event after the engine stop event by:
 initiating a fueling event whereby fueling to the engine is enabled and the engine starts and its speed increases to an idle speed over a start period; and   in response to initiating the fueling event, commanding the valve control system to control the intake/exhaust valves of the cylinders to mitigate or eliminate NVH caused by engine jerk over the start period.   
     
     
         6 . A valve control method for stop/start events of an engine of a vehicle, the method comprising:
 providing a valve control system configured for full lift control of respective intake and exhaust valves of a plurality of cylinders of the engine; and   performing, by a controller of the engine, an engine stop event including:
 initiating a fuel shutoff (FSO) event whereby fueling to the engine is disabled and the engine fully stops after a stop period, and 
 in response to initiating the FSO event, commanding the valve control system to close each intake valve prior to closing its respective exhaust valve to:
 (i) expel any residual gases from the cylinders during respective exhaust strokes prior to closing the respective exhaust valves, and 
 (ii) prevent air-only intake and compression within the cylinders during the stop period to thereby mitigate or eliminate noise/vibration/harshness (NVH) caused by the air-only intake and compression. 
 
   
     
     
         7 . The valve control method of  claim 6 , wherein the commanding of the valve control system comprises closing each exhaust valve after the exhaust stroke of its respective cylinder. 
     
     
         8 . The valve control method of  claim 6 , wherein the commanding of the valve control system comprises fully closing the intake valves followed by fully closing the respective exhaust valves for the remainder of the stop period until the engine stop event is complete. 
     
     
         9 . The valve control method of  claim 6 , further comprising commanding, by the controller, the valve control system to close every intake valve of the engine prior to closing every respective exhaust valve of the engine to prevent both (i) residual in-cylinder gases and (ii) air-only in-cylinder compression during subsequent exhaust strokes to thereby mitigate or eliminate NVH; and wherein the NVH is caused by engine jerk corresponding to cylinder pressure increases caused by the air-only intake and compression. 
     
     
         10 . The valve control method of  claim 6 , further comprising performing, by the controller, an engine start event after the engine stop event by:
 initiating a fueling event whereby fueling to the engine is enabled and the engine starts and its speed increases to an idle speed over a start period; and   in response to initiating the fueling event, commanding the valve control system to control the intake/exhaust valves of the cylinders to mitigate or eliminate NVH caused by engine jerk over the start period.